AirHint found the following cheapest return flights from Helsinki (HEL) to Basel (BSL) in September 2025 (see full year).

Return flights

17 Sep - 26 Sep	Lufthansa
15 Sep - 10 Oct	Lufthansa
18 Sep - 22 Sep	Norwegian Air Sweden AOC
28 Sep - 03 Oct	Norwegian Air Sweden AOC
26 Sep - 03 Oct	Lufthansa
12 Sep - 16 Sep	Ryanair
25 Sep - 06 Oct	Norwegian Air Sweden AOC
19 Sep - 28 Sep	Lufthansa
26 Sep - 28 Sep	Lufthansa
20 Sep - 30 Sep	KLM
12 Sep - 14 Sep	Norwegian Air Sweden AOC
01 Sep - 08 Sep	Scandinavian Airlines
05 Sep - 12 Sep	Norwegian Air Sweden AOC
04 Sep - 07 Sep	Air France

Also check the deals for one-way flights from Helsinki to Basel in September.

The deals are updated regularly. The prices may go up as tickets are purchased by other travellers. Only the cheapest flights are offered. Select a price to book and secure these cheap prices.

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Cheapest return flights from Helsinki to Basel in September from $203

Return flights